Immediate and long-term career goals. Transduction of anti-HIV components into hematopoietic stem cell (HSC) provides great promise for the treatment of AIDS and the development of a therapeutic AIDS vaccine. The current ex-vivo manipulation and expansion of stem cells by using recombinant cytokines generally results in a decrease of in vivo repopulation or a loss of HSC multipotentiality. Progress in this area needs elaboration of defined stem cell cycle conditions and knowledge of HIV replication. The candidate of this award plans to broaden her scientific background in stem cell research, and to study the physiologic role of a cell cycle checkpoint protein p21 ciplNvAF1/sd_l (hereafter p21) in HSC cycling as well as in transduction efficiency with HIV derived vectors. Once the K18 award is completed, the trainee plans to collaborate with the sponsor to develop gene therapy strategies to generate HSC and therefore CD4+ T cells which are resistant to the pathogenic effects of HIV-1. Outline of the research plan. Gene therapy of AIDS, the strategy of transferring anti-HIV genes into HSC, has been one of the great yet unfulfilled premises of recent years, since the efficiency of transduction is moderate (30 - 65% with HIV derived vectors) and the cells which remain to carry transfected genes are extremely low in vivo, such as 0.1-1% in animals and in human (4,21,33). The cycle status of HSC plays a cardinal role in efficiency of transduction and in hematopoietic cell re-population. A single molecule, p21, is able to dictate stem cell kinetics in vivo (15), and in its absence, stem cells leave a quiescent stage and enter the cell cycle (15). We hypothesize that modification of the cell cycle checkpoint molecule, p21, can release HSC from quiescence into cycling, and this may increase transduction efficiency without loss of multipotentiality. To test this hypothesis we plan to: 1) employ the RNAi technique to silence p21 gene expression in HSC; and 2) use different in vitro and in vivo models to determine the transduction efficiency and HSC multipotentiality after transduction with vectors commonly used in gene therapy strategies. The objective of this application is to enable a junior investigator to broaden her scientific background, in particular, to use stem cells in her research. This K18 award will give her an opportunity to apply the knowledge of stem cell cycling to HIV/AIDS research and to find the better ways of prevention or cure of HIV/AIDS.